Process of manufacturing hard porous electrodes for batteries.



y UNITED STAT Iatented Maj Q4, 1964.?

PATENT OFF E.

, HEINRICHPAUL RUDOLF LUDWIG PoRscKE AND GUSTAV ADOLPH WEDEKIND, orHAMBURae RMANY.

PROCESS'OF MANUFAQTURINGHARD POROUS ELECTRODES FOR BATTERIESSPECIFICATION forming part of Letters Patent No. 760,561, dated May 24,1904 Application filed November'lS, 1903. Serial No. 181,639- (Nospecimens.)

To all whom it map-y concern/.

Be it known that we, .I-IEINRIOILPAUL RU- DQLF LUDWIG PoRsoKE and GUSTAVADoLrH W EDEKIND, of Hamburg, Germany, have in-- vented certain new anduseful improvements in processes of treating metallic oxids or metallicpowders in such a manner that they can be used for the manufacture ofhard porous electrodes which do not dissolve in alkaline solutions, ofwhich the following is a full, clear, andexact description.

The process usually adopted for rendering metallic oxids durableconsists in either mixing them with sulfuric acid and allowing theresulting pulpy mass to harden or in adding muriatic acid to a mixtureof metallic oxids and carbon and allowing that mixture to become firm.

Another method consists in mixing oxid of copper with chlorid ofmagnesium and allowing the mixture to harden.

Oxid plates made in'accordance with the first-mentioned process-that is,hardened by the use of sulfuric acid-suffer from the disadvantage ofbeing soluble in water and in alkaline solutions. Consequently theycannot be used if an alkaline solution is the electrolyte employed. Theelectrode made in the second manner (mixing metallic oxids with carbonand hardening the mixture by adding muriatic acid) is discharged whendipped into the electrolyte. This is due to the circumstance that thereexists a potential difference between the particles of carbon and themetallic oxid employedfor instance, oxid of copperwhich potentialdifference tends to compensate. Further disadvantages resulting from theemployment of this method are that the admixture of non-depolarizingcarbon unnecessarily increases the weight of the elec-.

trode and that the mass of oxid which has been mixed with carbon andthen hardened becomes loose as soon as the oxid has been reduced tometal.

The third method (mixing the metallic oxid-for instance, oxid ofcopperwith chlorid ofmagnesium) cannot be employed,becauseoxid-of-copper electrodes which have been hardened by means of chloridof magnesium the oxygen and the chlorin.

either by using it as a cathode or by reducing 8 5 when reduced to metalin an alkaline electro- 5 Moreover, the crumbling away or peeling off ofthe mass of oxid very easily results in shortcuiting between electrodesof different polarity.

The process which forms the subject of the present invention consists inhardening pure 6O metallic oxids or pure metallic powders to which noforeign additions whatever have been madeby means of chlorin compoundsof whatever metal is used. Oxid of copper and finely-pulverized copperare very suitable sub: 5

stances to employ. By mixing them with a solution of protochlorid ofcopper they can be hardened to a firm porous electrically-conductingsubstance.

To give an example, oxid of copper is stirred 7 I to a fairly consistentpaste in a solution of protochlorid of copper and fine copper filings orshavings stirred into the paste, when cuprous chlorids will be formed.This paste is put into the molds, or if it is to be used for themanufacture of electrodes on suitable carriers or on copper plates thenthe molds, carriers, or plates are heated for about half an hour toabout 100 Celsius. After that time all thewater in the paste will haveevaporated and the paste will have become afirm porous mass of metallicoxid. When this is done, the plate is electrolyzed with the object ofsetting free This can be done it to metal in a suitable electrolyte witha metal plate occupying a higher position in the corresponding contactseries than the particular oxid plate employed and after this reoxidizedin the well-known manner by heat or 9 electrolysis.

An electrode made in accordance with this process by means of chlorid ofcopper does not dissolve in water or in alkaline solutions.

It does not discharge automatically and does not lose in bulk even afterinnumerable reductions and oxidations have taken place. On the contrary,the capacity and the potential of the electrode after each dischargefollowing oxidation remains the same as it was before the discharge.Experiments have shown that the mass remains firm and porous.Consequently an electrode made in accordance with this process can beused for a practically unlimited period. This cannot be said of anyelectrode made by any other known process, all such electrodes losingeffective mass, and therefore capacity, even during the first reduetion;

Having now described our invention, what we claim, and desire to secureby Letters Patent, is

A process for treating metallic oxids or metallic powders of thecharacter set forth, for the manufacture of hard porous electrodes whichdo not dissolve in alkaline solutions,

HEINRICH PAUL RUDOLF LUDWIG PURSCKE. GUSTAV ADOLPH WEDEKlNl);

Witnesses:

H. C. HELLMRIOH, T. Umus'r. HAFERMANN.

